Effects of Metformin Delivery via Biomaterials on Bone and Dental Tissue Engineering

Human periodontal ligament stem cells and metformin to enhance periodontal regeneration in rats

BACKGROUND

Effective periodontal repair and regeneration remain a critical clinical need, requiring strategies that address the complex regeneration of both bone and cementum within the periodontal complex. The objectives of this study were to: (1) develop a novel strategy for periodontal regeneration via human periodontal ligament stem cells (hPDLSCs) and metformin; (2) investigate the metformin regulatory mechanism via the ERK1/2 signaling pathway that promotes periodontal regeneration; (3) evaluate the effectiveness of the combination of hPDLSCs and metformin in promoting the repair of periodontal defects in rats.

METHODS

hPDLSCs were cultured in medium with graded metformin doses (0-600 μM) to determine the optimal concentration via CCK-8 assay, scratch assay and osteogenic/cementogenic differentiation analyses. ERK1/2 phosphorylation, induced by the optimal metformin concentration, and its inhibition by U0126 (10 μM) were analyzed via Western blot to assess its role in promoting osteogenesis and cementogenesis. In vivo, 30 rats with periodontal defects were divided into five groups: (1) Blank control; (2) Matrigel only; (3) Matrigel + metformin; (4) Matrigel + hPDLSCs; (5) Matrigel + Metformin + hPDLSCs. Micro-CT and histological staining were performed at 6 weeks to evaluate periodontal regeneration. Data were analyzed using one-way and two-way ANOVA (p < 0.05).

RESULTS

100 μM metformin optimally promoted hPDLSCs proliferation, migration, osteogenesis, and cementogenesis, with ALP activity and mineralization increased by 5-fold and 17-fold, respectively, and cementogenic gene expression upregulated to 6-8 times control levels (p < 0.05). The MEK1/2 inhibitor (U0126) decreased metformin's impact on osteogenesis and cementogenesis by 40-50 % (p < 0.05). Compared to the control group, Matrigel+Met+hPDLSCs group enhanced bone regeneration by 3.6 folds, and increased cemental regeneration by 9.5 folds in rats (p < 0.05).

CONCLUSION

This study focused on the dual role of metformin-hPDLSCs combination in promoting both osteogenesis and cementogenesis, addressing the specific needs of periodontal complex regeneration. Additionally, the ERK1/2 signaling is involved in the metformin-induced osteogenesis and cementogenesis.

Advancements in 3D gel culture systems for enhanced angiogenesis in bone tissue engineering

Angiogenesis-osteogenesis coupling is a crucial process in bone tissue engineering, requiring a suitable material structure for vessel growth. Recently, the 3D culture system has gained significant attention due to its benefits in cell growth, proliferation and tissue regeneration. Its most notable advantage is its ECM-like function, which supports endothelial cell adhesion and facilitates the formation of vascular-like networks-crucial for angiogenesis-osteogenesis coupling. Hydrogels, with their highly hydrophilic polymer network resembling the extracellular matrix, make the 3D gel culture system an ideal approach for angiogenesis due to its cellular integrity and adjustable properties. This article reviews the current use of 3D gel culture systems in bone tissue engineering, covering substrates, characteristics and processing technologies, thereby offering readers profound insights into these systems.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Efficacy of adjunctive local periodontal treatment for type 2 diabetes mellitus patients with periodontitis: A systematic review and network meta-analysis

OBJECTIVES

To investigate the effectiveness of different adjunctive local treatments combined with non-surgical periodontal therapy (NSPT) to reduce pocket depth (PD), gain clinical attachment level (CAL), and/or reduce glycated hemoglobin (HbA1c) in individuals with both type 2 diabetes mellitus (T2DM) and periodontitis in a systematic review and network meta-analysis.

DATA SOURCES

Publications were searched in Cochrane databases, EMBASE, Google Scholar, MEDLINE, PubMed, opengrey.eu, and www.

CLINICALTRIALS

gov up to May 29, 2024 with no language restriction.

STUDY SELECTION

Only randomized controlled trials (RCTs) were included. Network meta-analysis utilized frequentist models.

DATA

The network meta-analysis of 30 RCTs involving 1224 patients revealed that, in short-term (2-3 months) and medium-term (4-6 months), adjunctive local treatment involving statins or metformin significantly outperformed scaling and root planning (SRP) with/without additional interventions such as photodynamic and laser therapies (PDT/LT), phytotherapy, doxycycline, bisphosphonates, antibiotics, antiseptics, or placebo for reducing PD and/or gaining CAL. In the long-term (>6 months), statins yielded the most significant additional PD reduction and CAL gain, followed by antibiotics, compared to SRP with antiseptics or placebo. Only PDT/LT demonstrated significantly greater HbA1c reduction in the short term compared to SRP with/without statins, antiseptics, or placebo.

CONCLUSION

This study moderately supports that adding metformin or statins locally to NSPT may enhance PD reduction and CAL gain compared to SRP with/without placebo.

CLINICAL SIGNIFICANCE

Clinicians are guided to optimize adjunctive therapies, enhancing the health of patients with type 2 diabetes and periodontitis. A strategic approach is proposed to tackle systemic and oral health challenges simultaneously.

Injectable porous microspheres for articular cartilage regeneration through in situ stem cell recruitment and macrophage polarization

In situ mesenchymal stem cells (MSCs) regenerative therapy holds promising potential for treating osteoarthritis. However, MSCs engraftment and intra-articular inflammation limit the therapeutic efficacy of this approach. This study introduces porous microspheres (PMs) composed of aldehyde-modified poly(lactic-co-glycolic acid), that encapsulate platelet derived growth factor-AB and kartogenin. Metformin (Met) is also incorporated onto the microsphere through a Schiff base reaction to create PMs@Met. In vitro, in vivo and ex experiments revealed that PMs@Met can be injected into the joint cavity, effectively recruiting endogenous MSCs in situ. This approach creates a favorable environment for MSCs proliferation. It also controls the intra-articular inflammatory environment by modulating the polarization of synovial macrophages, ultimately promoting cartilage repair. In summary, our study presents an innovative tissue engineering strategy for the treatment of osteoarthritis-induced articular cartilage injuries. STATEMENT OF SIGNIFICANCE: Cell therapy using autologous mesenchymal stem cells (MSCs) has potential to slow the progression of osteoarthritis (OA). Nonetheless, there are some disadvantages to adopting in situ MSCs therapy, including difficulties with MSC engraftment into cartilage-deficient regions, the effect of intra-articular inflammation on MSC therapeutic efficacy, and attaining selective chondrogenic MSC differentiation. We created injectable PLGA microspheres (PMs) that were loaded with PDGF-AB and KGN. Metformin was bonded to the surface of microspheres using a Schiff base reaction. The microspheres can recruit intra-articular MSCs and encourage their development into chondrocytes. The microspheres actively modulate the inflammatory joint environment by altering synovial macrophage polarization, thereby supporting MSCs in effective cartilage treatment. To summarize, microspheres hold great potential in the treatment of OA.

Metformin-mediated effects on mesenchymal stem cells and mechanisms: proliferation, differentiation and aging

Mesenchymal stem cells (MSCs) are a type of pluripotent adult stem cell with strong self-renewal and multi-differentiation abilities. Their excellent biological traits, minimal immunogenicity, and abundant availability have made them the perfect seed cells for treating a wide range of diseases. After more than 60 years of clinical practice, metformin is currently one of the most commonly used hypoglycaemic drugs for type 2 diabetes in clinical practice. In addition, metformin has shown great potential in the treatment of various systemic diseases except for type 2 diabetes in recent years, and the mechanisms are involved with antioxidant stress, anti-inflammatory, and induced autophagy, etc. This article reviews the effects and the underlying mechanisms of metformin on the biological properties, including proliferation, multi-differentiation, and aging, of MSCs in vitro and in vivo with the aim of providing theoretical support for in-depth scientific research and clinical applications in MSCs-mediated disease treatment.

T. gondii excretory proteins promote the osteogenic differentiation of human bone mesenchymal stem cells via the BMP/Smad signaling pathway

BACKGROUND

Bone defects, resulting from substantial bone loss that exceeds the natural self-healing capacity, pose significant challenges to current therapeutic approaches due to various limitations. In the quest for alternative therapeutic strategies, bone tissue engineering has emerged as a promising avenue. Notably, excretory proteins from Toxoplasma gondii (TgEP), recognized for their immunogenicity and broad spectrum of biological activities secreted or excreted during the parasite's lifecycle, have been identified as potential facilitators of osteogenic differentiation in human bone marrow mesenchymal stem cells (hBMSCs). Building on our previous findings that TgEP can enhance osteogenic differentiation, this study investigated the molecular mechanisms underlying this effect and assessed its therapeutic potential in vivo.

METHODS

We determined the optimum concentration of TgEP through cell cytotoxicity and cell proliferation assays. Subsequently, hBMSCs were treated with the appropriate concentration of TgEP. We assessed osteogenic protein markers, including alkaline phosphatase (ALP), Runx2, and Osx, as well as components of the BMP/Smad signaling pathway using quantitative real-time PCR (qRT-PCR), siRNA interference of hBMSCs, Western blot analysis, and other methods. Furthermore, we created a bone defect model in Sprague-Dawley (SD) male rats and filled the defect areas with the GelMa hydrogel, with or without TgEP. Microcomputed tomography (micro-CT) was employed to analyze the bone parameters of defect sites. H&E, Masson and immunohistochemical staining were used to assess the repair conditions of the defect area.

RESULTS

Our results indicate that TgEP promotes the expression of key osteogenic markers, including ALP, Runx2, and Osx, as well as the activation of Smad1, BMP2, and phosphorylated Smad1/5-crucial elements of the BMP/Smad signaling pathway. Furthermore, in vivo experiments using a bone defect model in rats demonstrated that TgEP markedly promoted bone defect repair.

CONCLUSION

Our results provide compelling evidence that TgEP facilitates hBMSC osteogenic differentiation through the BMP/Smad signaling pathway, highlighting its potential as a therapeutic approach for bone tissue engineering for bone defect healing.

Ag2 O-TiO2 -NTs enhance osteogenic activity in vitro by modulating TNF-α/β-catenin signaling in bone marrow-derived mesenchymal stem cells

The toxic effects of nanoparticles-silver oxide (Ag2 O) limited its use. However, loading Ag2 O nanoparticles into titanium dioxide (TiO2 ) nanotubes (Ag2 O-TiO2 -NTs) has more efficient biological activity and safety. The aim of this study was to observe the effect of Ag2 O-TiO2 -NTs on osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) and its mechanism. The enzyme activity of lactate dehydrogenase (LDH) and the expression of RUNX family transcription factor 2 (Runx2), OPN, OCN in BMSCs were detected by quantitative real time polymerase chain reaction. At 14 days of induction, the mineralization ability and alkaline phosphatase (ALP) activity of cells in each group were observed by Alizarin Red S staining and ALP staining. In addition, the protein levels of tumor necrosis factor-α (TNF-α) and β-catenin in BMSCs of each group were observed by western blot. After 14 days of the induction, the mineralization ability and ALP activity of BMSCs in the Ag2 O-TiO2 -NTs group were significantly enhanced compared with those in the Ag2 O and TiO2 groups. Western blot analysis showed that the BMSCs in the Ag2 O-TiO2 -NTs group exhibited much lower protein level of TNF-α and higher protein level of β-catenin than those in the Ag2 O and TiO2 groups.Ag2 O-TiO2 -NTs enhance the osteogenic activity of BMSCs by modulating TNF-α/β-catenin signaling.

3D Elastomeric Stent Functionalized with Antioxidative and Perivascular Tissue Regenerative Activities Ameliorated PVT Deprivation-Induced Vein Graft Failure

Clinically, arterial injuries are always accompanied with perivascular tissue damage, which may contribute to high failure rate of vein grafts due to intimal hyperplasia and acute thrombosis. In this study, a "perivascular tissue (PVT) deprivation" animal model is constructed to mimic clinical scenarios and identify the contribution of arterial PVT to the success of vein grafts. Proteomics analysis suggests that depriving PVT may exacerbate reactive oxygen species (ROS)-induced endothelial apoptosis by up-regulating inflammation response and oxidative stress. Locally administering metformin on vein grafts through 3D-printed external stent (PGS-PCL) shows antioxidative and anti-inflammatory properties to protect cells from ROS invasion, thereafter decreasing acute thrombosis. Moreover, metformin induce rapid regeneration of perivascular adipose tissue in recipient regions, which improves patency by inhibiting intimal hyperplasia. Proteomics, western blot, and in vitro blocking tests reveal that metformin resists endothelial apoptosis through AMPK/mTOR and NFκB signaling pathways. To conclude, PVT deprivation exacerbates inflammatory response and oxidative stress in vein grafts bridging arterial circulation. Metformin-loaded stent ameliorates "PVT damage" related vein graft failure, and enhances patency of through resisting endothelial apoptosis and regenerating arterial PVAT, offering a promising avenue to improve the success of vein grafts in clinic.

Multi-scale, multi-level anisotropic silk fibroin/metformin scaffolds for repair of peripheral nerve injury

Silk fibroin (SF) as a natural polymer has a long history of application in various regenerative medicine fields, but there are still many shortcomings in silk fibroin for using as nerve scaffolds, which limit its clinical application in peripheral nerve regeneration (PNR). In this work, a multi-scale and multi-level metformin (MF)-loaded silk fibroin scaffold with anisotropic micro-nano composite topology was prepared by micromolding electrospinning for accelerating PNR. The scaffolds were characterized for morphology, wettability, mechanical properties, degradability, and drug release, and Schwann cells (SCs) and dorsal root ganglia (DRG) were cultured on the scaffolds to assess their effects on neural cell behavior. Finally, the gene expression differences of neural cells cultured on scaffolds were analyzed by gene sequencing and RT-qPCR to explore the possible signaling pathways and mechanisms. The results showed that the scaffolds had excellent mechanical properties and hydrophilicity, slow degradation rate and drug release rate, which were enough to support the repair of peripheral nerve injury for a long time. In Vitro cell experiments showed that the scaffolds could significantly promote the orientation of SCs and axons extension of DRG. Gene sequencing and RT-qPCR revealed that the scaffolds could up-regulate the expression of genes related to SCs proliferation, adhesion, migration, and myelination. In summary, the scaffolds hold great potential for promoting PNR at the micro/nano multiscale and physical/chemical levels and show promising application for the treatment of peripheral nerve injury in the future.

Mechanism behind the Upregulation of Proteins Associated with the NLRP3 Inflammasome in Periodontitis and Their Role in the Immune Response in Diabetes—A Systematic Review

Background: The molecular crosstalk between periodontitis and diabetes is well established. The role of the NLRP3 inflammasome, a multicomponent inflammatory machinery, is an emerging field of research on the relationship between these two uncommunicable diseases. Recent advances are revealing further molecular details regarding the biological function and the mechanism behind the NLRP3 inflammasome dysregulation and highlighting an unexpected role for the caspase-1 in immune homeostasis. We aimed to understand which metabolic checkpoints are involved in contributing to and instigating the relationship between periodontitis and diabetes. We tried to explore the involvement of the NLRP3 in regulating the cytokine-chemokines profile and discussed the potential synergism in these mechanisms when these two diseases coexist in the same patient. Methods: A literature search was carried out in the electronic databases (MEDLINE, EMBASE, and Cochrane Library) for relevant studies from inception until January 2022 for trials and cohort studies that investigated the activation and regulation mechanism of the NLRP3 inflammasome in patients with periodontitis and type two diabetes. Two investigators independently extracted data. The data quality assessment was rated by the Joanna Briggs Institute (JBI). Results: from twenty-six references identified, three studies (two case-control and one cross-sectional) met the inclusion criteria. Analysis of periodontal tissue samples in diabetic individuals exhibited significant overexpression of the NLRP3 inflammasome when compared with healthy controls. Conclusions: there is insufficient evidence to sustain the involvement of the upregulation of genes and proteins involved in the activation of NLRP3 inflammasome components in patients with periodontitis and diabetes.

mTOR Signaling Pathway in Bone Diseases Associated with Hyperglycemia

The interplay between bone and glucose metabolism has highlighted hyperglycemia as a potential risk factor for bone diseases. With the increasing prevalence of diabetes mellitus worldwide and its subsequent socioeconomic burden, there is a pressing need to develop a better understanding of the molecular mechanisms involved in hyperglycemia-mediated bone metabolism. The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that senses extracellular and intracellular signals to regulate numerous biological processes, including cell growth, proliferation, and differentiation. As mounting evidence suggests the involvement of mTOR in diabetic bone disease, we provide a comprehensive review of its effects on bone diseases associated with hyperglycemia. This review summarizes key findings from basic and clinical studies regarding mTOR's roles in regulating bone formation, bone resorption, inflammatory responses, and bone vascularity in hyperglycemia. It also provides valuable insights into future research directions aimed at developing mTOR-targeted therapies for combating diabetic bone diseases.